fix(bienvenida): match body/bullet type sizes and clip the logo mark

Tier 4 visual fidelity, audit 14.4/14.5/14.6/14.8 (t4 lines 693-701):
body copy is 14.5px (was bodyMedium's 14), bullet titles are
13.5px/w800 and subtitles 11.5px (was 14/w800 and 12), the gap between
bullets tightens from 16 to 12, and the 76x76 logo mark is now clipped
to a 20px rounded rect instead of painted square.

lib/pantallas/pantalla_bienvenida.dart

@@ -71,17 +71,23 @@ class PantallaBienvenida extends StatelessWidget {
                       child: Column(
                         crossAxisAlignment: CrossAxisAlignment.stretch,
                         children: [
-                          Image.asset(
+                          // Audit 14.8 (t4 line 693): the prototype clips
-                            'assets/icons/pluriwave_app_mark.png',
+                          // its logo mark to a 20px rounded rect; the build
-                            key: const ValueKey('welcome-logo'),
+                          // used to paint it square.
-                            width: 76,
+                          ClipRRect(
-                            height: 76,
+                            borderRadius: BorderRadius.circular(20),
-                            errorBuilder:
+                            child: Image.asset(
-                                (_, __, ___) => Icon(
+                              'assets/icons/pluriwave_app_mark.png',
-                                  Icons.graphic_eq_rounded,
+                              key: const ValueKey('welcome-logo'),
-                                  size: 76,
+                              width: 76,
-                                  color: t.electricMagenta,
+                              height: 76,
-                                ),
+                              errorBuilder:
+                                  (_, __, ___) => Icon(
+                                    Icons.graphic_eq_rounded,
+                                    size: 76,
+                                    color: t.electricMagenta,
+                                  ),
+                            ),
                           ),
                           const SizedBox(height: 22),
                           Text(
@@ -95,7 +101,10 @@ class PantallaBienvenida extends StatelessWidget {
                           const SizedBox(height: 12),
                           Text(
                             l10n.welcomeBody,
+                            // Audit 14.4 (t4 line 697): 14.5px, not
+                            // bodyMedium's 14.
                             style: theme.textTheme.bodyMedium?.copyWith(
+                              fontSize: 14.5,
                               color: theme.colorScheme.onSurface.withValues(
                                 alpha: 0.72,
                               ),
@@ -109,14 +118,16 @@ class PantallaBienvenida extends StatelessWidget {
                             titulo: l10n.welcomeBullet1Title,
                             subtitulo: l10n.welcomeBullet1Subtitle,
                           ),
-                          const SizedBox(height: 16),
+                          // Audit 14.6 (t4 line 701): 12px between bullets,
+                          // not 16.
+                          const SizedBox(height: 12),
                           FilaCaracteristicaBienvenida(
                             icon: Icons.directions_car_rounded,
                             iconColor: t.liveGreen,
                             titulo: l10n.welcomeBullet2Title,
                             subtitulo: l10n.welcomeBullet2Subtitle,
                           ),
-                          const SizedBox(height: 16),
+                          const SizedBox(height: 12),
                           FilaCaracteristicaBienvenida(
                             icon: Icons.alarm_rounded,
                             iconColor: t.warmCoral,
@@ -196,13 +207,18 @@ class FilaCaracteristicaBienvenida extends StatelessWidget {
             children: [
               Text(
                 titulo,
+                // Audit 14.5 (t4 line 700): 13.5px/w800, not bodyMedium's
+                // 14/w800.
                 style: theme.textTheme.bodyMedium?.copyWith(
+                  fontSize: 13.5,
                   fontWeight: FontWeight.w800,
                 ),
               ),
               Text(
                 subtitulo,
+                // Audit 14.5 (t4 line 700): 11.5px, not bodySmall's 12.
                 style: theme.textTheme.bodySmall?.copyWith(
+                  fontSize: 11.5,
                   color: theme.colorScheme.onSurface.withValues(alpha: 0.58),
                 ),
               ),

test/pantallas/pantalla_bienvenida_test.dart

@@ -65,6 +65,74 @@ void main() {
     },
   );
 
+  testWidgets(
+    'visual fidelity (audit 14.4/14.5): body copy is 14.5px, bullet titles '
+    'are 13.5px/w800, bullet subtitles are 11.5px (t4 lines 697/700-702)',
+    (tester) async {
+      final navegacion = EstadoNavegacionRaiz();
+      addTearDown(navegacion.dispose);
+
+      await tester.pumpWidget(_app(navegacion: navegacion));
+      await tester.pumpAndSettle();
+
+      final l10n = lookupAppLocalizations(const Locale('es'));
+
+      final body = tester.widget<Text>(
+        find.textContaining('53.412 emisoras de 238 países'),
+      );
+      expect(body.style?.fontSize, 14.5);
+
+      final tituloBullet = tester.widget<Text>(
+        find.text(l10n.welcomeBullet1Title),
+      );
+      expect(tituloBullet.style?.fontSize, 13.5);
+      expect(tituloBullet.style?.fontWeight, FontWeight.w800);
+
+      final subtituloBullet = tester.widget<Text>(
+        find.text(l10n.welcomeBullet1Subtitle),
+      );
+      expect(subtituloBullet.style?.fontSize, 11.5);
+    },
+  );
+
+  testWidgets(
+    'visual fidelity (audit 14.6): the 3 feature bullets are spaced 12px '
+    'apart, not 16 (t4 line 701)',
+    (tester) async {
+      final navegacion = EstadoNavegacionRaiz();
+      addTearDown(navegacion.dispose);
+
+      await tester.pumpWidget(_app(navegacion: navegacion));
+      await tester.pumpAndSettle();
+
+      final bullets = find.byType(FilaCaracteristicaBienvenida);
+      final gap =
+          tester.getTopLeft(bullets.at(1)).dy -
+          tester.getBottomLeft(bullets.at(0)).dy;
+      expect(gap, 12);
+    },
+  );
+
+  testWidgets(
+    'visual fidelity (audit 14.8): the logo mark is clipped to a 20px '
+    'rounded rect, not painted square (t4 line 693)',
+    (tester) async {
+      final navegacion = EstadoNavegacionRaiz();
+      addTearDown(navegacion.dispose);
+
+      await tester.pumpWidget(_app(navegacion: navegacion));
+      await tester.pumpAndSettle();
+
+      final clip = tester.widget<ClipRRect>(
+        find.ancestor(
+          of: find.byKey(const ValueKey('welcome-logo')),
+          matching: find.byType(ClipRRect),
+        ),
+      );
+      expect(clip.borderRadius, BorderRadius.circular(20));
+    },
+  );
+
   testWidgets('rendered content contains no monetization strings', (
     tester,
   ) async {